Audio reproduction equipment for driving one or more speakers include a power amplifier circuit or stage for amplifying an audio signal in order to drive the speakers. Typically, such a power amplifier utilizes power transistors as amplification devices. In fact, power MOSFETS have been shown to provide improved performance as compared to other types of transisters.
An example of an audio power amplifier circuit utilizing power MOSFETS is disclosed in Hochstein et al, U.S. Pat. No. 4,483,016. The circuit includes P-type MOSFET's which are controlled by an audio signal to alternately couple a positive voltage power supply and a negative voltage power supply to a speaker. This circuit requires the use of two power supplies, one of which supplies the positive voltage and the other of which supplies the negative voltage. The use of two power supplies increases the size and cost of the overall circuit.
Velazquez, U.S. Pat. No. 4,464,634 discloses a an audio power amplifier circuit similar to that in Hochstein et al, replacing the two power supplies with a single power source. However, two high voltage rectifier circuits are required to provide a positive voltage and a negative voltage. Such a construction results in the duplication of the rectifier components increasing the size and cost of the unit.
The present invention is intended to overcome these and other problems associated with audio power amplifier circuits.